Clara M Korstjens

Publications of Clara M Korstjens

• Low-intensity pulsed ultrasound affects RUNX2 immunopositive osteogenic cells in delayed clinical fracture healing.

  Authors: Sjoerd Rutten, Peter A Nolte, Clara M Korstjens, Jenneke Klein-Nulend

  Bone. 08/2009;

  INTRODUCTION: Osteogenic cell proliferation and differentiation play an important role in adequate fracture healing, and is target for osteoinductive therapies in delayed fracture healing. The aim ofINTRODUCTION: Osteogenic cell proliferation and differentiation play an important role in adequate fracture healing, and is target for osteoinductive therapies in delayed fracture healing. The aim of this study was to investigate whether low-intensity pulsed ultrasound enhances fracture healing at the tissue level in patients with a delayed union of the osteotomized fibula through an effect on the presence of RUNX2 immunopositive osteogenic cells. The effect was studied in both atrophic and hypertrophic delayed unions. MATERIALS AND METHODS: Biopsies were obtained from 6 female and 1 male patient (age 43-63) with a delayed union of the osteotomized fibula after a high tibial osteotomy treated for 2-4 months with or without low-intensity pulsed ultrasound in a randomized prospective double-blind placebo-controlled trial. Immunolocalization of RUNX2 protein was performed to identify osteogenic cells. Histomorphometrical analysis was performed to determine the number of cells expressing RUNX2 located within and around the newly formed woven bone at the fracture end (area of new bone formation), and up to 3 mm distant from the fracture end. RESULTS: Cells expressing RUNX2 were present in all histological sections of control and low-intensity pulsed ultrasound-treated bone evaluated. Within the area of new bone formation, RUNX2 immunopositive cells were found in the undifferentiated soft connective tissue, at the bone surface (presumably osteoblasts), and within the newly formed woven bone. Low-intensity pulsed ultrasound treatment of fibula delayed unions significantly reduced the number of RUNX2 immunopositive cells within the soft connective tissue at the fracture ends, whereas the number of RUNX2 immunopositive cells at the bone surface was not affected. The number of RUNX2 immunopositive cells was similar for the atrophic and hypertrophic delayed unions. CONCLUSIONS: Immunolocalization of RUNX2 positive cells in delayed unions of the fibula reveals that delayed clinical fracture healing does not result in impairment of osteogenic cell proliferation and/or differentiation at the tissue level, even if delayed unions are clinically regarded as atrophic. Reduced number of osteogenic RUNX2 immunopositive cells within the soft connective tissue, and unchanged number of RUNX2 immunopositive cells at the bone surface, implicate that low-intensity pulsed ultrasound does not increase osteogenic cell presence, but likely affects osteogenic cell differentiation.

• Low-intensity pulsed ultrasound increases bone volume, osteoid thickness and mineral apposition rate in the area of fracture healing in patients with a delayed union of the osteotomized fibula.

  Authors: Sjoerd Rutten, Peter A Nolte, Clara M Korstjens, Marion A van Duin, Jenneke Klein-Nulend

  Bone. 09/2008; 43(2):348-54.

  INTRODUCTION: Low-intensity pulsed ultrasound (LIPUS) accelerates impaired fracture healing, but the exact mechanism is unknown. The aim of this study was to investigate how LIPUS affects boneINTRODUCTION: Low-intensity pulsed ultrasound (LIPUS) accelerates impaired fracture healing, but the exact mechanism is unknown. The aim of this study was to investigate how LIPUS affects bone healing at the tissue level in patients with a delayed union of the osteotomized fibula, by using histology and histomorphometric analysis to determine bone formation and bone resorption parameters. MATERIALS AND METHODS: Biopsies were obtained from 13 patients (9 female, 4 male; age 42-63) with a delayed union of the osteotomized fibula after a high tibial osteotomy, treated for 2-4 months with or without LIPUS in a randomized prospective double-blind placebo-controlled trial. In the histological sections of the delayed union biopsies, 3 areas of interest were distinguished, i.e. 1) area of new bone formation at the fracture ends, 2) area of cancellous bone, and 3) area of cortical bone. Histomorphometrical analysis was performed to determine bone formation and bone resorption parameters (as well as angiogenesis). RESULTS: In LIPUS-treated delayed unions, endosteal callus formation by direct bone formation without a cartilage intermediate as well as indirect bone formation was observed, while in untreated controls only indirect bone formation was observed. In the area of new bone formation, LIPUS significantly increased osteoid thickness by 47%, mineral apposition rate by 27%, and bone volume by 33%. No increase in the number of blood vessels was seen in the newly formed bony callus. In the area of cancellous bone, bone volume was significantly increased by 17% whereas no effect on osteoid thickness and mineral apposition rate was seen. LIPUS did not affect osteoid volume, osteoid maturation time, number of osteocytes, osteocyte lacunae, or osteoclast-like cells in any of the areas of interest. CONCLUSIONS: Our results suggest that LIPUS accelerates clinical fracture healing of delayed unions of the fibula by increasing osteoid thickness, mineral apposition rate, and bone volume, indicating increased osteoblast activity, at the front of new bony callus formation. Improved stability and/or increased blood flow, but probably not increased angiogenesis, might explain the differences in ossification modes between LIPUS-treated delayed unions and untreated controls.